A CLOSER LOOK, by Kimball Garrett, White-crowned Sparrow

Closer-Look-White-crowned-Sparrows-illustration-by-Kimball-Garrett

Illustration by Kimball Garrett

Originally published in the Western Tanager Vol. 46 No. 4 December-January 1980

An abundant and familiar wintering bird through most of southern California, the White-crowned Sparrow (Zonotrichia leucophrys) actually shows a rather complex distribution in the region, with each of its four local subspecies having a unique seasonal role. This month we'll work on the recognition of these subspecies, with the usual admonition that intergradation and intra-population variation render a large number of individuals unassignable to race in the field even in the most well-marked forms.

Z. I. gambelii (the "Gambel's White-crowned") is the common wintering White-crown in the region, arriving in mid- to late-September (exceptionally in early September) and becoming quite abundant by the second week of October. A few gambelii may linger through mid-May, but this race summers in subarctic western North America.

Z. I. pugetensis (the "Puget Sound White-crown") is also strictly a winter visitant in the region, but it appears to be restricted to the coastal slope—mostly in the northern counties. It is probably overlooked because of its similarity to gambelii and especially, to the next race.

Z. I. nuttallii (the "Nuttall's White-crown") is a permanent resident along the immediate coastal strip from Pt. Conception north (it has nested as far south as Goleta); within its range it can be quite common. Its whistled song is a familiar sound, for example, at Morro Bay (look for the birds hopping around the base of Morro Rock), just as it is in downtown San Francisco

Z. I. oriantha (the "Mountain White-crowned") breed at or above timberline in the mountains of western North America. It has long been known to nest in the Sierra Nevada and the White Mountains, and a small breeding population was discovered around Mt. San Gorgonio in the San Bernardino Mtns. in the 1950s. The migration of this race is mostly through the deserts; spring migrants are usually noted in May, when the majority of gambelii individuals have departed. Only a few winter records exist, and these are generally from the south-eastern part of the region.

Nominate Z. I. leucophrys of Eastern North America has not been recorded in California, but its occurrence seems likely in light of the California occurrence of other birds with similar ranges. Nominate leucophrys cannot be told in the field from oriantha.

The following identification discussion deals only with adult birds. Young birds in their first fall and winter have the black and white crown stripes replaced by brown and buff. A molt of body feathers replaces these stripes with the adult pattern early in their first spring. Subspecific determination of immature birds in the field should not be attempted.

Oriantha is easily separated from other California races by its black lores. This pattern gives the race what Phillips (Birds of Arizona, 1964) calls an "imperious mien." The bill of oriantha averages somewhat larger than that of gambelii, and tends to be pinker (less orange). In oriantha, the white crown stripes often look quite broad and flared.

Our common race, gambelii, is quite gray like oriantha. However, it and the following races have white lores. This field mark should be noted carefully since its perception may depend on the arrangement of the facial feathers and on shadow.

The remaining races, nuttallii and pugetensis, cannot be told from each other in the field. They are both considerably browner than gambelii, being tinged on the breast, sides, back, and nape with this color. They also have brighter and more extensively brown flanks than does gambelii. Both nuttallii and pugetensis have a yellow carpal (bend-of-the-wing) area; this area is whitish in gambelii (but exceedingly difficult to see in the field). The beaks of nuttallii and pugetensis adults are yellowish (with the black tip characteristic of all races). Bill color is a poor mark on immature birds.

Since White-crowned Sparrows routinely sing on their winter grounds, song can be an important clue in distinguishing wintering gambelii and pugetensis. The lazy, buzy songs (without clear whistled trills) that are so familiar in winter throughout southern California belong to gambelii. Clearly different are the sweeter trilled songs of nuttallii and pugetensis. Practice learning the songs of nuttallii along the central California coast in summer; pugetensis will sound similar, but again remember that most populations have their own unique dialects. And beware another complication: A White-crown on its winter grounds may learn the songs of resident White-crowns, and vice versa! Nevertheless, the best way to distinguish wintering pugetensis in southern California is by the nuttallii-like song. 


 

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